HTML5 has many elements that enable developers to create well-structured and varied websites. CSS is a style sheet language that defines how HTML elements are displayed. By using a combination of HTML5 and CSS, developers can create rich, interactive applications. The HTML5 elements provide ways to separate a HTML document into divisions, create headers and footers, define sections, create headings, and define the body of the document. In addition, there are many HTML5 elements that allow the user to interact with the website, inputting information in various formats like dates, times, numbers, email addresses and much more. The data is sent to the browser by using HTML, and the design is applied to that data by using CSS. To be able to create the structure and style you want for your site, you must be familiar with both languages.